I tried out the HIIT 100s routine from the "forum which will not be named" and saw some great fat loss in 6 weeks. I wouldn't call it great "gains" in strength, as I'm just working back to previous strength, but the workouts were killer to say the least.

I believe the op is referencing Mentzer or Yates style high intenstiy training, which is doing a single, high intensity set for each exercise, as opposed to HIIT, which is cardio with intervals.